Capacitive sensing, in general, is a known technology. For instance, a “theremin” is a musical instrument that effectively uses capacitive sensing to control the sound from a speaker. Additionally, capacitive sensors have been used in airplanes as fuel level sensors; in automobile applications for occupant classification; and in appliances as touch sensors, smart phones, and other consumer goods.
Prior art systems and methods are available to measure dielectric constant and conductivity of a material. However, such systems and methods are expensive, particularly for measuring liquids with fairly high conductivities. For example, instruments are available that can measure the dielectric constant of a liquid, but they impose limits on the liquid's conductivity to less than 10 μS/cm (e.g., see the BI-870 Dielectric Constant Meter produced by Brookhaven Instruments Corporation).